This invention relates to absorbable polymeric materials possessing an enhanced ability for permanent deformation at room temperature through a crazing mechanism. This invention also relates to the use of these materials in medical device applications that require the material to be reshapable. One such application is in absorbable maxillofacial bone fixation plates where complex fracture site surface contours are often encountered. For comparison, see the Masterpiece.TM. maxillofacial bone plate system (Storz Instrument Co., MO 63122, USA). Another application is in absorbable surgical clips and staples where improved toughness and ductility are desirable.
The following U.S. Pat. Nos. are pertinent to the present inventions described in this application: 4,243,775, 4,279,249, 4,300,565, 4,539,981, 4,550,449, 4,744,365, 4,788,979, 4,839,130, 4,844,854. Also pertinent is the international patent application WO 89/05664. These patents and the application are incorporated herein by reference.
The modification of glassy polymeric materials for improved toughness is well known in the nonabsorbable polymer art. Perhaps the most notable example of a toughened glassy plastic is high impact polystyrene (HIPS). The following review article describes the property improvements of HIPS: Soderquist, M. E. and Dion, R. P., "High Impact Polystyrene," in Encyclopedia of Polymer Science and Engineering, Vol 16, pp. 88-97, John Wiley & Sons, New York, 1989. Many other nonabsorbable polymers have been modified for improved toughness or impact resistance. A general review of this field can be found in Yee, A. F., "Impact Resistant Materials," in Encyclopedia of Polymer Science and Engineering, Vol. 8, pp. 59-68, John Wiley & Sons, New York, 1989 and in Bucknall, C. B., Toughened Plastics, Applied Science Publishers, London, 1977 and in Comprehensive Polymer Sciences Vol. 2, section 15.3, pp. 526-532, C. Booth & C. Price, eds., Pergamon Press, New York, 1989. Generally, toughness and impact resistance have been improved by incorporating a discontinuous rubbery phase in the parent polymer matrix. This has been done by physical blending or by preparation of block or graft copolymers. Similar concepts have been applied to thermosets such as epoxy resins (see Yee, A. F. and Pearson, R. A., "Toughening Mechanisms in Elastomer-Modified Epoxies Part 1 Mechanical Studies," J. Mat. Sci., Vol. 21, 1986, pp. 2462-2474 and Pearson, R. A. and Yee, A. F., "Toughening Mechanisms in Elastomer-Modified Epoxies Part 2 Microscopy Studies," J. Mat. Sci., Vol. 21, 1986, pp. 2475-2488. All of the above cited disclosures are incorporated herein by reference. Although increases of ductility in nonabsorbable rubber modified plastics have been reported, the primary purpose of the modification has been to impart impact resistance and toughness. To our knowledge this property modification method has not been put to use in medical devices, either absorbable or nonabsorbable.
The U.S. Pat. Nos. 4,243,775 and 4,300,565 cited above disclose absorbable polymeric compositions which were thought to form a two phase morphology. These patents do not mention any enhancement of deformability in bending due to the presence of a rubbery phase.
Some other patents (U.S. Pat. Nos. 4,744,365, 4,839,130 and 4,844,854) disclose two phase copolymers of lactide and glycolide. These patents do not mention any enhancement of deformability in bending other than reduced brittleness. Also, the copolymers disclosed in the '365, '130 and '854 patents do not contain a rubbery phase; rather, they contain two semicrystalline glassy phases. The utility of these two phase copolymers are described as a surgical clip or staple. The rubber toughened materials of this application may also be useful as a surgical clip or staple.
None of the prior art mentions the usefulness of materials which can be permanently deformed at room temperature through crazing as a medical device. The U.S. Pat. No. 4,279,249 claims bioabsorbable boneplate devices manufactured from a copolymer of at least 90% units derived from lactic acid and reinforcing fibers made of polyglycolic acid or a copolymer thereof. Nowhere in this patent is it disclosed that the material can be permanently deformed by bending at room temperature, although improved resilience and shock resistance are disclosed. Also, this patent claims a "matrix" polymer of at least 90% lactic acid units.
The present invention describes medical devices made from block copolymers. The block copolymer is composed of a lactide or a lactide/glycolide copolymer and a low glass transition temperature or a rubbery polymer such as polytrimethylene carbonate. It is the presence of the rubbery or soft block which imparts the deformability in bending to the surgical repair devices described in this application.
Other bioabsorbable bone fixation devices have been fashioned from high molecular weight poly(1-lactide); see, e.g. U.S. Pat. Nos. 4,539,981 and 4,550,449. This material does not allow reshaping at room temperature and no mention of such a property is made in these patents.
Block copolymers containing trimethylene carbonate and lactide were exemplified in the international patent application WO 89/05664. The materials exemplified were higher compared to the compositions described in this application in rubbery phase content. In the WO application, no mention was made of ductile properties or the usefulness of such a property in medical devices.
Block copolymers containing trimethylene carbonate, caprolactone, and glycolide as well as block copolymers containing caprolactone and glycolide were exemplified for use as suture coatings in U.S. Pat. No. 4,788,979. These materials were also rich in soft phase forming units. No mention was made of ductile properties in this patent.
The following embodiments summarize the invention:
1. An article of manufacture comprising a deformable surgical repair device, the deformable surgical repair device manufactured from a copolymer, the copolymer selected from the group consisting of a block and graft copolymer, the copolymer comprising a plurality of first linkages selected from the group consisting of glycolic acid ester and lactic acid ester linkages, and mixtures thereof, and a plurality of second linkages selected from the group consisting of 1,3-dioxan-2-one; 1,4-dioxan-2-one and .epsilon.-caprolactone linkages, the plurality of first linkages comprising at least about 50 up to about 90 mole percent of the copolymer.
2. The article of embodiment 1 wherein the copolymer is a block copolymer.
3. The article of embodiment 2 wherein the plurality of first linkages comprises lactic acid ester linkages.
4. The article of embodiment 2 wherein the plurality of first linkages comprises glycolic acid ester linkages.
5. The article of embodiment 3 or 4 wherein the plurality of second linkages comprises 1,3-dioxan-2-one linkages.
6. An article of manufacture comprising a deformable fracture fixation device, the deformable fracture fixation device manufactured from a copolymer, the copolymer selected from the group consisting of a block and graft copolymer, the copolymer having a plurality of first linkages comprising lactic acid ester linkages and a plurality of second linkages selected from the group consisting of 1,3-dioxan-2-one and 1,4-dioxan-2-one linkages, the plurality of lactic acid ester linkages comprising more than 50 to about 80 weight percent of the copolymer.
7. The article of embodiment 6 wherein the copolymer is a block copolymer.
8. The article of embodiment 7 wherein the plurality of lactic acid ester linkages comprises about 80 weight percent of the copolymer.
9. The article of embodiment 8 wherein the plurality of second linkages comprises 1,3-dioxan-2-one linkages.
10. An article of manufacture comprising a deformable surgical repair device, the deformable surgical repair device manufactured from a blend of a first and a second absorbable polymer, the first absorbable polymer comprising a plurality of linkages selected from the group consisting of glycolic acid ester and lactic acid ester linkages, and mixtures thereof, and the second absorbable polymer comprising a plurality of linkages selected from the group consisting of 1,3-dioxan-2-one; 1,4-dioxan-2-one and .epsilon.-caprolactone linkages, the first absorbable polymer comprising at least about 50 up to about 90 weight percent of the blend.
11. The article of embodiment 10 wherein the first absorbable polymer is a homopolymer.
12. The article of embodiment 11 wherein the first absorbable homopolymer consists essentially of lactic acid ester linkages.
13. The article of embodiment 10 wherein the first absorbable polymer is a copolymer.
14. The article of embodiment 12 wherein the second absorbable polymer comprises a plurality of linkages selected from the group consisting of 1,3-dioxan-2-one and 1,4-dioxan-2-one linkages.
15. The article of embodiments 1, 2, 3, 10, 11, 12 or 14 wherein the deformable surgical repair device is a fracture fixation device.
16. The article of embodiment 15 wherein the fracture fixation device is a bone plate.
17. The article of embodiments 1, 2, 3, 10, 11, 12 or 14 wherein the deformable surgical repair device is a clip.
18. The article of embodiments 1, 2, 3, 10, 11, 12 or 14 wherein the deformable surgical repair device is a staple.
19. A surgical composite structure for mammalian tissue comprising:
a) a reinforcing component prepared from a plurality of fibers, plurality of the fibers manufactured from a biocompatible polymer, and PA1 b) a bioabsorbable component comprising a copolymer PA1 a) a reinforcing component prepared from a plurality of fibers, plurality of the fibers manufactured from biocompatible polymer, and PA1 b) a bioabsorbable component comprising a blend of a first and second absorbable polymer, the first absorbable polymer comprising a plurality of linkages selected from the group consisting of glycolic acid ester and lactic acid ester linkages, and mixtures thereof, and the second absorbable polymer comprising a plurality of linkages selected from the group consisting of 1,3-dioxan-2-one; 1,4-dioxan-2-one and .epsilon.-caprolactone linkages, the first absorbable polymer comprising at least about 50 up to about 90 weight percent of the blend. PA1 A. Hard phase forming monomers PA1 B. Soft phase forming monomers PA1 A. Hard phase forming polymers PA1 B. Soft phase forming polymers
the copolymer selected from the group consisting of a block and graft copolymer, the copolymer comprising a plurality of first linkages selected from the group consisting of glycolic acid aster and lactic acid ester linkages, and mixtures thereof, and a plurality of second linkages selected from the group consisting of 1,3-dioxan-2-ons; 1,4-dioxan-2-one and .epsilon.-caprolactone linkages, the plurality of first linkages comprising at least about 50 up to about 90 mole percent of the copolymer.
20. The structure of embodiment 19 wherein the reinforcing component is manufactured from an absorbable biocompatible polymer.
21. The structure of embodiment 20 wherein the absorbable biocompatible polymer is selected from the group consisting of a homopolymer or copolymer of polyglycolic acid, polylactic acid, polyhydroxy butyrate and blends of the same, and poly(d-lactic acid) blended with poly(1-lactic acid).
22. The structure of embodiment 19 wherein the reinforcing component is manufactured from a nonabsorbable biocompatible polymer.
23. The structure of embodiment 22 wherein the nonabsorbable biocompatible polymer is selected from the group consisting of polyethylene terephthalate, silk, nylon, polypropylene, polyethylene and polyoxymethylene and blends of the same.
24. The structure of embodiment 19, 20, 21, 22 or 23 wherein the bioabsorbable Component comprises a block copolymer.
25. The structure of embodiment 24 wherein the plurality of first linkages in the block copolymer comprises lactic acid ester linkages.
26. The structure of embodiment 24 wherein the plurality of first linkages in the block copolymer comprises glycolic acid ester linkages.
27. The structure of embodiment 25 or 26 wherein the plurality of second linkages in the block copolymer comprises 1,3-dioxan-2-one linkages.
28. A surgical composite structure for mammalian tissue comprising:
29. The structure of embodiment 19 wherein the reinforcing component is manufactured from an absorbable biocompatible polymer.
30. The structure of embodiment 20 wherein the absorbable biocompatible polymer is selected from the group consisting of a homopolymer or copolymer of polyglycolic acid, polylactic acid, polyhydroxy butyrate and blends of the same, and poly(d-lactic acid) blended with poly(1-lactic acid).
31. The structure of embodiment 19 wherein the reinforcing component is manufactured from a nonabsorbable biocompatible polymer.
32. The structure of embodiment 22 wherein the nonabsorbable biocompatible polymer is selected from the group consisting of polyethylene terephthalate, silk, nylon, polypropylene, polyethylene and polyoxymethylene and blends of the same.
33. The structure of embodiment 28, 29, 30, 31 or 32 wherein the first absorbable polymer in the bioabsorbable component is a homopolymer.
34. The structure of embodiment 33 wherein the first absorbable homopolymer in the bioabsorbable component consists essentially of lactic acid ester linkages.
35. The structure of embodiment 28, 29, 30, 31 or 32 wherein the first absorbable polymer in the bioabsorbable component is a copolymer.
36. The structure of embodiment 24 wherein the second absorbable polymer in the bioabsorbable component comprises a plurality of linkages selected from the group consisting of 1,3-dioxan-2-one and 1,4-dioxan-2-one linkages.
Referring to the embodiments in subparagraphs 5, 6, 9, 10 and 14, above, and generally as described in this specification, some polymers have been described as linkages of one or more monomers. Some of these monomers are described as cyclic esters, e.g. 1,4-dioxan-2-one. It is to be understood that any person skilled in the art implicitly knows how to make and how to use these monomers to form the polymer linkages and that, therefore, the description of these linkages by the use of this monomeric nomenclature is adequate.
Referring to the embodiments in subparagraphs 1, 6, 10 and 15, above, it is to be clearly understood that the surgical repair and fracture fixation devices include, but are not limited to, those embodiments described in subparagraphs 16 to 18, above. Thus, other devices, e.g. a bone pin, bone rod, bone screw, trocar, prosthetic tubular article, and similar or related molded or extruded devices, are within the scope of this invention. For a general disclosure of medical uses, see columns 4 and 5 in U.S. Pat. No. 4,135,622 issued Jan. 23, 1979, which is incorporated herein by reference.
Referring to subparagraphs 19 and 28, above, the plurality of fibers in the reinforcing component can be matted, chopped, woven, knitted, unidirectional or a fiber tow. The plurality of fibers can also be composed of laminated plies wherein each ply consists of continuous, unidirectional fibers, woven fabric or knitted fabric and the direction of fibers between adjacent plies need not be the same.
Referring, generally, to subparagraphs 19 to 36, above, in the fabrication of the composite structure, it is to be understood that the melting point of the bioabsorbable component must be less than the melting point of the reinforcing component. See also, generally, Example 12.
Referring to the embodiments in subparagraphs 20 and 29, above, it is to be understood that other absorbable polymers can be used beside those described in subparagraphs 21 and 30, above, respectively, other absorbable polymers include those described in the "Description of the Invention," below, subparagraphs 1A. 2A., which description is not exclusive.